Discovering Earth’s History Rocks record geological events and changing life forms of the past. We have learned that Earth is much older than anyone had previously imagined and that its surface and interior have been changed by the same geological processes that continue today. Rocks Record Earth History
Discovering Earth’s History Uniformitarianism means that the forces and processes that we observe today have been at work for a very long time. A Brief History of Geology
What causes rocks to be disturbed? Unconformities • An unconformity represents a long period during which deposition stopped, erosion removed previously formed rocks, and then deposition resumed.
• An angular unconformity indicates that during the pause in deposition, a period of deformation (folding or tilting) and erosion occurred.